The benefits of plastic for fences which are used where they are subject to weathering and corrosion are generally well recognized. Fences using much materials are light weight, strong, and attractive. They can be made with color integrated into the material so that they do not need frequent painting during their use, and possibly their greatest asset is the inherent weather resistance of the materials. A plastic structure such as a fence post can be expected to last as long as anyone wants it to, even in the most severe environment, with no sign of deterioration, and it will not require any maintenance.
However, to attain the economy available from such materials, most plastic fence posts are manufactured as hollow structures, and then relatively expensive fittings are required to attach them to a base structure such as a wooden floor. Furthermore, since the typical floor flange is attached to the hollow plastic post with bolts or other fasteners which penetrate holes near the bottom of the post, the post structure is subjected to severe stress at the holes when any forces are applied transverse to the post. Thus, the force of anyone leaning on the fence post or on a cross rail which transmits force to the post my cause a hollow post to crack at the flange attachment holes.
One structure which can be used to overcome such failures is a long socket into which the post fits. Such a structure spreads the force over a larger area and prevents stress fractures. However, such socket type fittings are both costly and unsightly. The beauty and the simplicity of a simple straight post is lost when a complex structure must be used around a large section at the bottom of the post to strengthen it and attach it to a floor.